Abstract: The calculation of secondary electron is one of the main research content of Kaufman discharge chamber. This paper is aimed at establishing non uniform steady discharge model to solving the secondary electron temperature. Non uniform steady discharge model starts from diffusion equation，we emphases the consideration of the effect of ion diffusion motion and ambipolar electron field to discharge chamber radial density gradient. Furthermore，consider the particle conservation equation，it can obtain the analytical representation for solving the secondary electron temperature. Using the typical date of Kaufman discharge chamber，the calculation illustrates that the result of non uniform steady discharge model is according with experiment result，at the same time，it also illustrates that in mid-pressure discharge condition or lower，diffusion motion and ambipolar electric field are the key facts which affects the discharge performance.